1. Field of the Invention
This invention relates to an ink jet recording apparatus and a discharge recovery apparatus used in said apparatus.
2. Related Background Art
For a recording apparatus, which conventionally records on a recording medium (hereinafter called "recording sheet" or simply "paper") such as paper and sheet for OHP, forms of mounting a recording head using any of various recording methods have been proposed. This recording head has various methods such as wire dot, thermal, thermal transfer, and ink jet methods.
Especially the ink jet method directly jets ink on a recording sheet, and draws attention as a quiet recording method with low running cost.
In a recording apparatus using the ink jet method, a recording head, in which fine discharge ports have been arranged, is generally used. When air bubble or dust enters the discharge port, or when ink has become unsuitable for discharge or recording owing to thickening caused by evaporation of ink solvent, etc., and the like, the state of discharge is maintained or recovered by the following: refreshing the ink by recovering the suction through the discharge port or by predischarging, or allowing some discharge ports, which are not concerned in discharge during recording, to discharge ink in order to maintain all discharge ports in a condition suitable for discharging always.
As a form of the means to maintain and recover the discharge, there is a recording apparatus provided with a cap member capable of covering the discharge port formation surface of the recording head, and with suction means such as pump means which communicates with this cap member and applies a suction force to the discharge port of the recording head.
The factor for improper discharge is removed together with the ink by discharging ink (predischarge, idle discharge) by driving an ink discharge energy generating element inside the discharge port while the cap is opposed to the discharge port formation surface, or by forcibly discharging ink by sucking ink through the discharge port by applying the suction force while the discharge port formation surface is covered with the cap.
In an appropriate position of the apparatus, on the other hand, there is a waste ink tank provided to store waste ink produced by the above-mentioned discharge recovery process.
To lead, into the waste ink tank, the ink received in a discharge recovery apparatus including the cap, pump and waste ink tube communicating these, etc. by the discharge recovery process, a so-called "idle suction" operation, in which the pump is operated while the cap is opened to air, is performed.
This is a very effective operation to prevent remaining waste ink from hardening, and prevent waste ink from leaking outward from the cap when the ink, received within the discharge recovery device by the discharge recovery process, is left to stand alone.
In these processes, however, an amount of ink to be discharged by predischarge, for example, an amount of ink to be discharged by idle discharge or an amount of ink to be exhausted by suction are respectively different because their objectives are respectively different. Nevertheless, an operation of pump means to recover exhausted ink was similar in any, of these processes.
In this case, in idle discharge, for example, which is performed by also allowing also discharge ports, which are not used, midway during recording to be used for discharging, a duration, in which the recording head remains at a nonrecording position, is long. To cope with high speed recording by improving the throughput, it takes a considerable time to maintain and recover, and high speed recording as a whole cannot be accomplished.
Also when a piston type pump was used, ink trapped by an absorber provided within the cap was recovered by repeating the full stroke several times. In this method, however, there were some cases where ink remains in an area far away from the recovery port though ink near the recovery port is well recovered.
In other words, although ink near the recovery port is quickly recovered by driving the piston, ink in an area far away from the recovery port takes time to move to near the recovery port, and cannot fully move only by the suction operation - driving the piston was terminated before the ink moves. As a result, the ink remained in the absorber. Such an existence of such residual ink was likely to cause fixing within the absorber.
Also the number of times for discharge recovery process to be started differs in accordance with frequency in use and product life that vary with the application and the like of the ink jet recording apparatus. In other words, in a recording apparatus with a use application, in which a large amount of waste ink is required, a large capacity of waste ink tank will be required. This is because the volume, which the waste ink tank occupies within the apparatus, becomes larger.
On the other hand, however, miniaturized recording apparatus has been advancing in recent years, and therefore an appropriate ingenuity should be exerted in securing the capacity of the waste ink tank.